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    <title>ShellCheck: SC3009 – In POSIX `sh`, brace expansion is undefined.</title>
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    <h1>SC3009 – ShellCheck Wiki</h1>
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    <h2 id="in-posix-sh-brace-expansion-is-undefined">In POSIX
<code>sh</code>, brace expansion is undefined.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC3009.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/sh</span></span>
<span id="cb1-2"><a href="SC3009.html#cb1-2" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb1-3"><a href="SC3009.html#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span> i <span class="kw">in</span> <span class="dt">{</span><span class="dv">1</span><span class="dt">..</span><span class="dv">5</span><span class="dt">}</span><span class="kw">;</span> <span class="cf">do</span> <span class="ex">...</span></span></code></pre></div>
<p>Here, <code>$i</code> expands to <code>{1..5}</code>. It does
<strong>not</strong> expand to the sequence <code>1 2 3 4 5</code></p>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC3009.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/sh</span></span>
<span id="cb2-2"><a href="SC3009.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="va">i</span><span class="op">=</span>1</span>
<span id="cb2-3"><a href="SC3009.html#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="co"># while $i ≤ 5 ...</span></span>
<span id="cb2-4"><a href="SC3009.html#cb2-4" aria-hidden="true" tabindex="-1"></a><span class="cf">while</span> <span class="bu">[</span> <span class="st">&quot;</span><span class="va">${i}</span><span class="st">&quot;</span> <span class="ot">-le</span> 5 <span class="bu">]</span><span class="kw">;</span> <span class="cf">do</span> <span class="ex">...</span></span>
<span id="cb2-5"><a href="SC3009.html#cb2-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb2-6"><a href="SC3009.html#cb2-6" aria-hidden="true" tabindex="-1"></a>  <span class="co"># something that will occur 5 times</span></span>
<span id="cb2-7"><a href="SC3009.html#cb2-7" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb2-8"><a href="SC3009.html#cb2-8" aria-hidden="true" tabindex="-1"></a>  <span class="va">i</span><span class="op">=</span><span class="va">$((i</span> <span class="op">+</span> <span class="dv">1</span><span class="va">))</span></span>
<span id="cb2-9"><a href="SC3009.html#cb2-9" aria-hidden="true" tabindex="-1"></a><span class="cf">done</span></span></code></pre></div>
<p>You can also use the <code>seq</code> command, e.g.
<code>seq 1 5</code>, but <code>seq</code> is not a POSIX utility.</p>
<h3 id="rationale">Rationale:</h3>
<h3 id="exceptions">Exceptions:</h3>
<p>None</p>
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